Support for multi-valued attributes in rlm_cache

[Arran Cudbard-Bell]

> I've been working the past days on adding support for multi-valued
> attributes in rlm_cache.

Thanks.

> Before I send a pull request, I'll be glad if you could review my work
> and report if I need to correct anything.

Reviewed and left line comments on your commit.

> What's currently supported :
> 
>  attr <op> 'string value'
>  attr <op> "xlat expanded value"
>  attr :=|+= attr-name
> 
> Code available here :
> https://github.com/olivierbeytrison/freeradius-server/tree/rlm_cache-update
> 
> I also wanted to know if it is "allowed" to have multiple identical
> attributes with the SET operator in a list.

If people want to do multiple set operations that's fine. I mean yeah it's pointless, but it doesn't seem worth adding extra code to prevent it.

> When are enforced the logic
> behind the operators ? when the radius packet is being crafted ?

No, it'd done when the pairs are moved between the cache list and the request_list with radius_pairmove.

You need to add checks for operators and value types into cache_verify.

-Arran